1. Field of the Invention
The present invention relates to a method of and an apparatus for measuring the strength of ultrasonic waves used with an ultrasonic cleaner that applies ultrasonic waves to an object soaked in a cleaning liquid in a cleaning tank, to wash the object.
2. Description of Related Art
The information technology (IT) industry is renovated every day. Precision parts incorporated in various devices related to the IT industry must have high cleanliness.
To highly clean the precision parts, ultrasonic cleaning is widely used. In the ultrasonic cleaning, it applies ultrasonic waves to an object immersed in a cleaning liquid in a cleaning tank, to produce cavitation that removes dust particles from the surface of the object. The cavitation is a phenomenon created when ultrasonic waves are applied to an object soaked in a liquid and produces very small bubbles around the object, the bubbles being compressed to collapse and generate shock waves that remove dust particles from the surface of the object.
When washing precision parts with ultrasonic waves, it is required to strictly manage the cleanliness of the precision parts.
For this, a related art such as Japanese Unexamined Patent Application Publication No, H06-137931 puts a sound pressure meter in a cleaning liquid, measures an ultrasonic wave strength with the sound pressure meter, and based on the measured ultrasonic wave strength, manages the cleanliness of an object to wash.
This related art directly measures the strength of ultrasonic waves with the sound pressure meter immersed in a cleaning liquid, and therefore, the sound pressure meter is affected by shock waves created by cavitation caused by the ultrasonic waves. The shock waves may remove dust particles from the surface of the object but they may damage the sound pressure meter itself.
The related art, therefore, needs frequent maintenance including replacement of the sound pressure meter, to increase costs.